## Derek Parfit

Print publication date: 1986

Print ISBN-13: 9780198249085

Published to Oxford Scholarship Online: November 2003

DOI: 10.1093/019824908X.001.0001

Show Summary Details
Page of

PRINTED FROM OXFORD SCHOLARSHIP ONLINE (www.oxfordscholarship.com). (c) Copyright Oxford University Press, 2019. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use.  Subscriber: null; date: 23 October 2019

# Why Our Identity Is not What Matters

Chapter:
(p.245) 12 Why Our Identity Is not What Matters
Source:
Reasons and Persons
Publisher:
Oxford University Press
DOI:10.1093/019824908X.003.0012

# Abstract and Keywords

Presents actual cases of brain bisection; how we might be able to divide and reunite our minds; what explains the unity of consciousness at any time; the imagined case of full division, in which each half of our brain would be successfully transplanted into the empty skull of another body; why neither of the resulting people would be us; why this would not matter, since our relation to each of these people contains what matters in the prudential sense, giving us reasons to care about these people, which are like our reasons to care about our own future;and how it is hard to believe that personal identity, or our own continued existence, is not what matters.

# 87. Divided Minds

Why Our Identity Is not What Matters 87. Divided Minds

Some recent medical cases provide striking evidence in favour of the Reductionist View. Human beings have a lower brain and two upper hemispheres, which are connected by a bundle of fibres. In treating a few people with severe epilepsy, surgeons have cut these fibres. The aim was to reduce the severity of epileptic fits, by confining their causes to a single hemisphere. This aim was achieved. But the operations had another unintended consequence. The effect, in the words of one surgeon, was the creation of ‘two separate spheres of consciousness’.33

This effect was revealed by various psychological tests. These made use of two facts. We control our right arms with our left hemispheres, and vice versa. And what is in the right halves of our visual fields we see with our left hemispheres, and vice versa. When someone's hemispheres have been disconnected, psychologists can thus present to this person two different written questions in the two halves of his visual field, and can receive two different answers written by this person's two hands.

Here is a simplified version of the kind of evidence that such tests provide. One of these people is shown a wide screen, whose left half is red and right half is blue. On each half in a darker shade are the words, ‘How many colours can you see?’ With both hands the person writes, ‘Only one’. The words are now changed to read, ‘Which is the only colour that you can see?’ With one of his hands the person writes ‘Red’, with the other he writes ‘Blue’.

If this is how this person responds, there seems no reason to doubt that he is having visual sensations—that he does, as he claims, see both red and blue. But in seeing red he is not aware of seeing blue, and vice versa. This is why the surgeon writes of ‘two separate spheres of consciousness’. In each of his centres of consciousness the person can see only a single colour. In one centre, he sees red, in the other, blue.

The many actual tests, though differing in details from the imagined test that I have just described, show the same two essential features. In seeing what is in the left half of his visual field, such a person is quite unaware of what he is now seeing in the right half of his visual field, and vice versa. And in the centre of consciousness in which he sees the left half of his visual field, (p.246) and is aware of what he is doing with his left hand, this person is quite unaware of what he is doing with his right hand, and vice versa.

One of the complications in the actual cases is that for most people, in at least the first few weeks after the operation, speech is entirely controlled by the right‐handed hemisphere. As a result, ‘if the word “hat” is flashed on the left, the left hand will retrieve a hat from a group of concealed objects if the person is told to pick out what he has seen. At the same time he will insist verbally that he saw nothing.’34 Another complication is that, after a certain time, each hemisphere can sometimes control both hands. Nagel quotes an example of the kind of conflict which can follow:

A pipe is placed out of sight in the patient's left hand, and he is then asked to write with his left hand what he was holding. Very laboriously and heavily, the left hand writes the letters P and I. Then suddenly the writing speeds up and becomes lighter, the I is converted to an E, and the word is completed as PENCIL. Evidently the left hemisphere has made a guess based on the appearance of the first two letters, and has interfered . . . But then the right hemisphere takes over control of the hand again, heavily crosses out the letters ENCIL, and draws a crude picture of a pipe.35

Such conflict may take more sinister forms. One of the patients complained that sometimes, when he embraced his wife, his left hand pushed her away.

Much has been made of another complication in the actual cases, hinted at in Nagel's example. The left hemisphere typically supports or ‘has’ the linguistic and mathematical abilities of an adult, while the right hemisphere ‘has’ these abilities at the level of a young child. But the right hemisphere, though less advanced in these respects, has greater abilities of other kinds, such as those involved in pattern recognition, or musicality. It is assumed that, after the age of three or four, the two hemispheres follow a ‘division of labour’, with each developing certain abilities. The lesser linguistic abilities of the right hemisphere are not intrinsic, or permanent. People who have had strokes in their left hemispheres often regress to the linguistic ability of a young child, but with their remaining right hemispheres many can re‐learn adult speech. It is also believed that, in a minority of people, there may be no difference between the abilities of the two hemispheres.

Suppose that I am one of this minority, with two exactly similar hemispheres. And suppose that I have been equipped with some device that can block communication between my hemispheres. Since this device is connected to my eyebrows, it is under my control. By raising an eyebrow I can divide my mind. In each half of my divided mind I can then, by lowering an eyebrow, reunite my mind.

This ability would have many uses. Consider

My Physics Exam. I am taking an exam, and have only fifteen minutes left in which to answer the last question. It occurs to me that there are two ways of tackling this question. I am unsure which is more likely to succeed. I therefore decide to divide my mind for ten minutes, to work in (p.247) each half of my mind on one of the two calculations, and then to reunite my mind to write a fair copy of the best result. What shall I experience?

When I disconnect my hemispheres, my stream of consciousness divides. But this division is not something that I experience. Each of my two streams of consciousness seems to have been straightforwardly continuous with my one stream of consciousness up to the moment of division. The only changes in each stream are the disappearance of half my visual field and the loss of sensation in, and control over, one of my arms.

Consider my experiences in my ‘right‐handed’ stream. I remember deciding that I would use my right hand to do the longer calculation. This I now begin. In working at this calculation I can see, from the movements of my left hand, that I am also working at the other. But I am not aware of working at the other. I might, in my right‐handed stream, wonder how, in my left‐handed stream, I am getting on. I could look and see. This would be just like looking to see how well my neighbour is doing, at the next desk. In my right‐handed stream I would be equally unaware both of what my neighbour is now thinking and of what I am now thinking in my left‐handed stream. Similar remarks apply to my experiences in my left‐handed stream.

My work is now over. I am about to reunite my mind. What should I, in each stream, expect? Simply that I shall suddenly seem to remember just having worked at two calculations, in working at each of which I was not aware of working at the other. This, I suggest, we can imagine. And, if my mind had been divided, my apparent memories would be correct.

In describing this case, I assumed that there were two separate series of thoughts and sensations. If my two hands visibly wrote out two calculations, and I also claimed later to remember two corresponding series of thoughts, this is what we ought to assume. It would be most implausible to assume that either or both calculations had been done unconsciously.

It might be objected that my description ignores ‘the necessary unity of consciousness’. But I have not ignored this alleged necessity. I have denied it. What is a fact must be possible. And it is a fact that people with disconnected hemispheres have two separate streams of consciousness—two series of thoughts and experiences, in having each of which they are unaware of having the other. Each of these two streams separately displays unity of consciousness. This may be a surprising fact. But we can understand it. We can come to believe that a person's mental history need not be like a canal, with only one channel, but could be like a river, occasionally having separate streams. I suggest that we can also imagine what it would be like to divide and reunite our minds. My description of my experiences in my Physics Exam seems both to be coherent and to describe something that we can imagine.

It might next be claimed that, in my imagined case, I do not have a (p.248) divided mind. Rather, I have two minds. This objection does not raise a real question. These are two ways of describing one and the same outcome.

A similar objection claims that, in these actual and imagined cases, the result is not a single person with either a divided mind or two minds. The result is two different people, sharing control of most of one body, but each in sole control of one arm. Here too, I believe that this objection does not raise a real question. These are again two ways of describing the same outcome. This is what we believe if we are Reductionists.

If we are not yet Reductionists, as I shall assume, we believe that it is a real question whether such cases involve more than a single person. Perhaps we can believe this in the actual cases, where the division is permanent. But this belief is hard to accept when we consider my imagined Physics Exam. In this case there are two streams of consciousness for only ten minutes. And I later seem to remember doing both of the calculations that, during these ten minutes, my two hands could be seen to be writing out. Given the brief and modest nature of this disunity, it is not plausible to claim that this case involves more than a single person. Are we to suppose that, during these ten minutes, I cease to exist, and two new people come into existence, each of whom then works out one of the calculations? On this interpretation, the whole episode involves three people, two of whom have lives that last for only ten minutes. Moreover, each of these two people mistakenly believes that he is me, and has apparent memories that accurately fit my past. And after these ten minutes I have accurate apparent memories of the brief lives of each of these two people, except that I mistakenly believe that I myself had all of the thoughts and sensations that these people had. It is hard to believe that I am mistaken here, and that the episode does involve three quite different people.

It is equally hard to believe that it involves two different people, with me doing one of the calculations, and some other person doing the other. I admit that, when I first divide my mind, I might in doing one of the calculations believe that the other calculation must be being done by someone else. But in doing the other calculation I might have the same belief. When my mind has been reunited, I would then seem to remember believing, while doing each of the calculations, that the other calculation must be being done by someone else. When I seem to remember both these beliefs, I would have no reason to think that one was true and the other false. And after several divisions and reunions I would cease to have such beliefs. In each of my two streams of consciousness I would believe that I was now, in my other stream, having thoughts and sensations of which, in this stream, I was now unaware.

# 88. What Explains the Unity of Consciousness?

Why Our Identity Is not What Matters 88. What Explains the Unity of Consciousness?

Suppose that, because we are not yet Reductionists, we believe that there must be a true answer to the question, ‘Who has each stream of (p.249) consciousness?’ And suppose that, for the reasons just given, we believe that this case involves only a single person: me. We believe that for ten minutes I have a divided mind.

Remember next the view that psychological unity is explained by ownership. On this view, we should explain the unity of a person's consciousness, at any time, by ascribing different experiences to this person, or ‘subject of experiences’. What unites these different experiences is that they are being had by the same person. This view is held both by those who believe that a person is a separately existing entity, and by some of those who reject this belief. And this view also applies to the unity of each life.

When we consider my imagined Physics Exam, can we continue to accept this view? We believe that, while my mind is divided, I have two separate series of experiences, in having each of which I am unaware of having the other. At any time in one of my streams of consciousness I am having several different thoughts and sensations. I might be aware of thinking out some part of the calculation, feeling writer's cramp in one hand, and hearing the squeaking of my neighbour's old‐fashioned pen. What unites these different experiences?

On the view described above, the answer is that these are the experiences being had by me at this time. This answer is incorrect. I am not just having these experiences at this time. I am also having, in my other stream of consciousness, several other experiences. We need to explain the unity of consciousness within each of my two streams of consciousness, or in each half of my divided mind. We cannot explain these two unities by claiming that all of these experiences are being had by me at this time. This makes the two unities one. It ignores the fact that, in having each of these two sets of experiences, I am unaware of having the other.

Suppose that we continue to believe that unity should be explained by ascribing different experiences to a single subject. We must then believe that this case involves at least two different subjects of experiences. What unites the experiences in my left‐handed stream is that they are all being had by one subject of experiences. What unites the experiences in my right‐handed stream is that they are all being had by another subject of experiences. We must now abandon the claim that ‘the subject of experiences’ is the person. On our view, I am a subject of experiences. While my mind is divided there are two different subjects of experiences. These are not the same subject of experiences, so they cannot both be me. Since it is unlikely that I am one of the two, given the similarity of my two streams of consciousness, we should probably conclude that I am neither of these two subjects of experiences. The whole episode therefore involves three such entities. And two of these entities cannot be claimed to be the kind of entity with which we are all familiar, a person. I am the only person involved, and two of these subjects of experiences are not me. Even if we assume that I am one of these two subjects of experiences, the other cannot be me, and is therefore not a person.

(p.250) We may now be sceptical. While the ‘subject of experiences’ was the person, it seemed plausible to claim that what unites a set of experiences is that they are all had by a single subject. If we have to believe in subjects of experiences that are not persons, we may doubt whether there really are such things. There are of course, in the animal world, many subjects of experiences that are not persons. My cat is one example. But other animals are irrelevant to this imagined case. On the view described above, we have to believe that the life of a person could involve subjects of experiences that are not persons.

Reconsider my experiences in my right‐handed stream of consciousness. In this stream at a certain time I am aware of thinking about part of a calculation, feeling writer's cramp, and hearing the sounds made by my neighbour's pen. Do we explain the unity of these experiences by claiming that they are all being had by the same subject of experiences, this being an entity which is not me? This explanation does not seem plausible. If this subject of experiences is not a person, what kind of thing is it? It cannot be claimed to be a Cartesian Ego, if I am claimed to be such an Ego. This subject of experiences cannot be claimed to be such an Ego, since it is not me, and this case involves only one person. Can this subject of experiences be a Cartesian Sub‐Ego, a persisting purely mental entity which is merely part of a person? We may decide that we have insufficient grounds for believing that there are such things.

I turn next to the other view mentioned above. Some people believe that unity is explained by ownership, even though they deny that we are separately existing entities. These people believe that what unites a person's experiences at any time is the fact that these experiences are being had by this person. As we have seen, in this imagined case this belief is false. While I am having one set of experiences in my right‐handed stream, I am also having another set in my left‐handed stream. We cannot explain the unity of either set of experiences by claiming that these are the experiences that I am having at this time, since this would conflate these two sets.

A Reductionist may now intervene. On his view, what unites my experiences in my right‐handed stream is that there is, at any time, a single state of awareness of these various experiences. There is a state of awareness of having certain thoughts, feeling writer's cramp, and hearing the sound of a squeaking pen. At the same time, there is another state of awareness of the various experiences in my left‐handed stream. My mind is divided because there is no single state of awareness of both of these sets of experiences.

It may be objected that these claims do not explain but only redescribe the unity of consciousness in each stream. In one sense, this is true. This unity does not need a deep explanation. It is simply a fact that several experiences can be co‐conscious, or be the objects of a single state of awareness. It may help to compare this fact with the fact that there is short‐term memory of experiences within the last few moments: short‐term memory of what is called ‘the specious present’. Just as there can be a single (p.251) memory of just having had several experiences, such as hearing a bell strike three times, there can be a single state of awareness both of hearing the fourth striking of this bell, and of seeing ravens fly past the bell‐tower. Reductionists claim that nothing more is involved in the unity of consciousness at a single time. Since there can be one state of awareness of several experiences, we need not explain this unity by ascribing these experiences to the same person, or subject of experiences.

It is worth restating other parts of the Reductionist View. I claim:

Because we ascribe thoughts to thinkers, it is true that thinkers exist. But thinkers are not separately existing entities. The existence of a thinker just involves the existence of his brain and body, the doing of his deeds, the thinking of his thoughts, and the occurrence of certain other physical and mental events. We could therefore redescribe any person's life in impersonal terms. In explaining the unity of this life, we need not claim that it is the life of a particular person. We could describe what, at different times, was thought and felt and observed and done, and how these various events were interrelated. Persons would be mentioned here only in the descriptions of the content of many thoughts, desires, memories, and so on. Persons need not be claimed to be the thinkers of any of these thoughts.

These claims are supported by the case where I divide my mind. It is not merely true here that the unity of different experiences does not need to be explained by ascribing all of these experiences to me. The unity of my experiences, in each stream, cannot be explained in this way. There are only two alternatives. We might ascribe the experiences in each stream to a subject of experiences which is not me, and, therefore, not a person. Or, if we doubt the existence of such entities, we can accept the Reductionist explanation. At least in this case, this may now seem the best explanation.

This is one of the points at which it matters whether my imagined case is possible. If we could briefly divide our minds, this casts doubt on the view that psychological unity is explained by ownership. As I argued, if we are not Reductionists, we ought to regard my imagined case as involving only a single person. It then becomes impossible to claim that the unity of consciousness should be explained by ascribing different experiences to a single subject, the person. We could maintain this view only by believing in subjects of experiences that are not persons. Other animals are irrelevant here. Our belief is about what is involved in the lives of persons. If we have to admit that in these lives there could be two kinds of subjects of experiences, those that are and those that are not persons, our view will have lost much of its plausibility. It would help our view if we could claim that, because persons are indivisible, my imagined case could never happen.

My case is imagined. But the essential feature of the case, the division of consciousness into separate streams, has happened several times. This (p.252) undermines the reply just given. My imagined case may well become possible, and could at most be merely technically impossible. And in this case the unity of consciousness in each stream cannot be explained by ascribing my experiences to me. Because this explanation fails, this case refutes the view that psychological unity can be explained by ascribing different experiences to a single person.

On the best known version of this view, we are Cartesian Egos. I defended Lichtenberg's objection to the Cartesian View. But that defence merely showed that we could not deduce, from the nature of our experiences, that we are such entities. I later claimed that there is no evidence in favour of this view, and much evidence against it. Since they support the argument just given, the actual cases of divided minds are further evidence against this view.

Descartes' view may be compared with Newton's belief in Absolute Space and Time. Newton believed that any physical event had its particular position solely in virtue of its relation to these two independent realities, Space and Time. We now believe that a physical event has its particular spatio‐temporal position in virtue of its various relations to the other physical events that occur. On the Cartesian View, a particular mental event occurs within a particular life solely in virtue of its ascription to a particular Ego. We can deny that the topography of ‘Mental Space’ is given by the existence of such persisting Egos. We can claim that a particular mental event occurs within some life in virtue of its relations to the many other mental and physical events which, by being interrelated, constitute this life.36

Another ground is sometimes given for belief in such Egos. It can be claimed against any wholly objective description of reality—any description not made from a ‘point of view’—that there are certain truths which it omits. One example of such a truth is that I am I, or that I am Derek Parfit. I am this particular person. These subjective truths may seem to imply that we are separately existing subjects of experiences.

Such truths can be stated by a Reductionist. The word ‘subjective’ is misleading. What are called subjective truths need not involve any subject of experiences. A particular thought may be self‐referring. It may be the thought that this particular thought, even if exactly similar to other thoughts that are thought, is still this particular thought—or this particular thinking of this thought. This thought is an impersonal but subjective truth.

Some would object that all of the other indexical concepts—such as ‘here’, ‘now’, and ‘this’—must be explained in a way that uses the concept ‘I’. This is not so. All of the others, including ‘I’, can be explained in a way that uses the self‐referring use of ‘this’. And this self‐referring use does not involve the notion of a self, or subject of experiences. It is the use of ‘this’ that in this sentence refers to this sentence. With this use of ‘this’, we can express ‘subjective’ truths without believing in the separate existence of subjects of experiences.37

# (p.253) 89. What Happens When I Divide?

Why Our Identity Is not What Matters 89. What Happens When I Divide?

I shall now describe another natural extension of the actual cases of divided minds. Suppose first that I am one of a pair of identical twins, and that both my body and my twin's brain have been fatally injured. Because of advances in neuro‐surgery, it is not inevitable that these injuries will cause us both to die. We have between us one healthy brain and one healthy body. Surgeons can put these together.

This could be done even with existing techniques. Just as my brain could be extracted, and kept alive by a connection with an artificial heart‐lung machine, it could be kept alive by a connection with the heart and lungs in my twin's body. The drawback, today, is that the nerves from my brain could not be connected with the nerves in my twin's body. My brain could survive if transplanted into his body, but the resulting person would be paralysed.

Even if he is paralysed, the resulting person could be enabled to communicate with others. One crude method would be some device, attached to the nerve that would have controlled this person's right thumb, enabling him to send messages in Morse Code. Another device, attached to some sensory nerve, could enable him to receive messages. Many people would welcome surviving, even totally paralysed, if they could still communicate with others. The stock example is that of a great scientist whose main aim in life is to continue thinking about certain abstract problems.

Let us suppose, however, that surgeons are able to connect my brain to the nerves in my twin's body. The resulting person would have no paralysis, and would be completely healthy. Who would this person be?

This is not a difficult question. It may seem that there is a disagreement here between the Physical and Psychological Criteria. Though the resulting person will be psychologically continuous with me, he will not have the whole of my body. But, as I have claimed, the Physical Criterion ought not to require the continued existence of my whole body.

If all of my brain continues both to exist and to be the brain of one living person, who is psychologically continuous with me, I continue to exist. This is true whatever happens to the rest of my body. When I am given someone else's heart, I am the surviving recipient, not the dead donor. When my brain is transplanted into someone else's body, it may seem that I am here the dead donor. But I am really still the recipient, and the survivor. Receiving a new skull and a new body is just the limiting case of receiving a new heart, new lungs, new arms, and so on.38

It will of course be important what my new body is like. If my new body was quite unlike my old body, this would affect what I could do, and might thus indirectly lead to changes in my character. But there is no reason to suppose that being transplanted into a very different body would disrupt my psychological continuity.

(p.254) It has been objected that ‘the possession of some sorts of character trait requires the possession of an appropriate sort of body’. Quinton answers this objection. He writes, of an unlikely case,

It would be odd for a six‐year old girl to display the character of Winston Churchill, odd indeed to the point of outrageousness, but it is not utterly inconceivable. At first, no doubt, the girl's display of dogged endurance, a world‐historical comprehensiveness of outlook, and so forth, would strike one as distasteful and pretentious in so young a child. But if she kept it up the impression would wear off.39

More importantly, as Quinton argues, this objection could show only that it might matter whether my brain is housed in a certain kind of body. It could not show that it would matter whether it was housed in any particular body. And in my imagined case my brain will be housed in a body which, though not numerically identical to my old body, is—because it is my twin's body—very similar.

On all versions of the Psychological Criterion, the resulting person would be me. And most believers in the Physical Criterion could be persuaded that, in this case, this is true. As I have claimed, the Physical Criterion should require only the continued existence of enough of my brain to be the brain of a living person, provided that no one else has enough of this brain. This would make it me who would wake up, after the operation. And if my twin's body was just like mine, I might even fail to notice that I had a new body.

It is in fact true that one hemisphere is enough. There are many people who have survived, when a stroke or injury puts out of action one of their hemispheres. With his remaining hemisphere, such a person may need to re‐learn certain things, such as adult speech, or how to control both hands. But this is possible. In my example I am assuming that, as may be true of certain actual people, both of my hemispheres have the full range of abilities. I could thus survive with either hemisphere, without any need for re‐learning.

I shall now combine these last two claims. I would survive if my brain was successfully transplanted into my twin's body. And I could survive with only half my brain, the other half having been destroyed. Given these two facts, it seems clear that I would survive if half my brain was successfully transplanted into my twin's body, and the other half was destroyed.

What if the other half was not destroyed? This is the case that Wiggins described: that in which a person, like an amoeba, divides.40 To simplify the case, I assume that I am one of three identical triplets. Consider

My Division. My body is fatally injured, as are the brains of my two brothers. My brain is divided, and each half is successfully transplanted into the body of one of my brothers. Each of the resulting people believes that he is me, seems to remember living my life, has my (p.255) character, and is in every other way psychologically continuous with me. And he has a body that is very like mine.

This case is likely to remain impossible. Though it is claimed that, in certain people, the two hemispheres may have the same full range of abilities, this claim might be false. I am here assuming that this claim is true when applied to me. I am also assuming that it would be possible to connect a transplanted half‐brain with the nerves in its new body. And I am assuming that we could divide, not just the upper hemispheres, but also the lower brain. My first two assumptions may be able to be made true if there is enough progress in neurophysiology. But it seems likely that it would never be possible to divide the lower brain, in a way that did not impair its functioning.

Does it matter if, for this reason, this imagined case of complete division will always remain impossible? Given the aims of my discussion, this does not matter. This impossibility is merely technical. The one feature of the case that might be held to be deeply impossible—the division of a person's consciousness into two separate streams—is the feature that has actually happened. It would have been important if this had been impossible, since this might have supported some claim about what we really are. It might have supported the claim that we are indivisible Cartesian Egos. It therefore matters that the division of a person's consciousness is in fact possible. There seems to be no similar connection between a particular view about what we really are and the impossibility of dividing and successfully transplanting the two halves of the lower brain. This impossibility thus provides no ground for refusing to consider the imagined case in which we suppose that this can be done. And considering this case may help us to decide both what we believe ourselves to be, and what in fact we are. As Einstein's example showed, it can be useful to consider impossible thought‐experiments.

It may help to state, in advance, what I believe this case to show. It provides a further argument against the view that we are separately existing entities. But the main conclusion to be drawn is that personal identity is not what matters.

It is natural to believe that our identity is what matters. Reconsider the Branch‐Line Case, where I have talked to my Replica on Mars, and am about to die. Suppose we believe that I and my Replica are different people. It is then natural to assume that my prospect is almost as bad as ordinary death. In a few days, there will be no one living who will be me. It is natural to assume that this is what matters. In discussing My Division, I shall start by making this assumption.

In this case, each half of my brain will be successfully transplanted into the very similar body of one of my two brothers. Both of the resulting people will be fully psychologically continuous with me, as I am now. What happens to me?

(p.256) There are only four possibilities: (1) I do not survive; (2) I survive as one of the two people; (3) I survive as the other; (4) I survive as both.

The objection to (1) is this. I would survive if my brain was successfully transplanted. And people have in fact survived with half their brains destroyed. Given these facts, it seems clear that I would survive if half my brain was successfully transplanted, and the other half was destroyed. So how could I fail to survive if the other half was also successfully transplanted? How could a double success be a failure?

Consider the next two possibilities. Perhaps one success is the maximum score. Perhaps I shall be one of the two resulting people. The objection here is that, in this case, each half of my brain is exactly similar, and so, to start with, is each resulting person. Given these facts, how can I survive as only one of the two people? What can make me one of them rather than the other?

These three possibilities cannot be dismissed as incoherent. We can understand them. But, while we assume that identity is what matters, (1) is not plausible. My Division would not be as bad as death. Nor are (2) and (3) plausible. There remains the fourth possibility: that I survive as both of the resulting people.

This possibility might be described in several ways. I might first claim: ‘What we have called “the two resulting people” are not two people. They are one person. I do survive this operation. Its effect is to give me two bodies, and a divided mind.’

This claim cannot be dismissed outright. As I argued, we ought to admit as possible that a person could have a divided mind. If this is possible, each half of my divided mind might control its own body. But though this description of the case cannot be rejected as inconceivable, it involves a great distortion in our concept of a person. In my imagined Physics Exam I claimed that this case involved only one person. There were two features of the case that made this plausible. The divided mind was soon reunited, and there was only one body. If a mind was permanently divided, and its halves developed in different ways, it would become less plausible to claim that the case involves only one person. (Remember the actual patient who complained that, when he embraced his wife, his left hand pushed her away.)

The case of complete division, where there are also two bodies, seems to be a long way over the borderline. After I have had this operation, the two ‘products’ each have all of the features of a person. They could live at opposite ends of the Earth. Suppose that they have poor memories, and that their appearance changes in different ways. After many years, they might meet again, and fail even to recognise each other. We might have to claim of such a pair, innocently playing tennis: ‘What you see out there is a single person, playing tennis with himself. In each half of his mind he mistakenly believes that he is playing tennis with someone else.’ If we are not yet Reductionists, we believe that there is one true answer to the question (p.257) whether these two tennis‐players are a single person. Given what we mean by ‘person’, the answer must be No. It cannot be true that what I believe to be a stranger, standing there behind the net, is in fact another part of myself.

Suppose we admit that the two ‘products’ are, as they seem to be, two different people. Could we still claim that I survive as both? There is another way in which we could. I might say: ‘I survive the operation as two different people. They can be different people, and yet be me, in the way in which the Pope's three crowns together form one crown.’41

This claim is also coherent. But it again greatly distorts the concept of a person. We are happy to agree that the Pope's three crowns, when put together, are a fourth crown. But it is hard to think of two people as, together, being a third person. Suppose the resulting people fight a duel. Are there three people fighting, one on each side, and one on both? And suppose one of the bullets kills. Are there two acts, one murder and one suicide? How many people are left alive? One or two? The composite third person has no separate mental life. It is hard to believe that there really would be such a third person. Instead of saying that the resulting people together constitute me—so that the pair is a trio—it is better to treat them as a pair, and describe their relation to me in a simpler way.

Other claims might be made. It might be suggested that the two resulting people are now different people, but that, before My Division, they were the same person. Before My Division, they were me. This suggestion is ambiguous. The claim may be that, before My Division, they together were me. On this account, there were three different people even before My Division. This is even less plausible than the claim I have just rejected. (It might be thought that I have misunderstood this suggestion. The claim may be that the resulting people did not exist, as separate people, before My Division. But if they did not then exist, it cannot have been true that they together were me.)

It may instead be suggested that, before My Division, each of the resulting people was me. After My Division, neither is me, since I do not now exist. But, if each of these people was me, whatever happened to me must have happened to each of these people. If I did not survive My Division, neither of these people survived. Since there are two resulting people, the case involves five people. This conclusion is absurd. Can we deny the assumption that implies this conclusion? Can we claim that, though each of the resulting people was me, what happened to me did not happen to these people? Assume that I have not yet divided. On this suggestion, it is now true that each of the resulting people is me. If what happens to me does not happen to X, X cannot be me.

There are far‐fetched ways to deny this last claim. These appeal to claims about tensed identity. Call one of the resulting people Lefty. I might ask, ‘Are Lefty and Derek Parfit names of one and the same person?’ For believers in tensed identity, this is not a proper question. As this shows, claims about tensed identity are radically different from the way in which (p.258) we now think. I shall merely state here what I believe others to have shown: these claims do not solve our problem.

David Lewis makes a different proposal. On his view, there are two people who share my body even before My Division. In its details, this proposal is both elegant and ingenious. I shall not repeat here why, as I have claimed elsewhere, this proposal does not solve our problem.42

I have discussed several unusual views about what happens when I divide. On these views, the case involves a single person, a duo, a trio two of whom compose the third, and a quintet. We could doubtless conjure up the missing quartet. But it would be tedious to consider more of these views. All involve too great distortions of the concept of a person. We should therefore reject the fourth suggested possibility: the claim that, in some sense, I survive as both of the two resulting people.

There are three other possibilities: that I shall be one, or the other, or neither of these people. These three claims seemed implausible. Note next that, as before, we could not find out what happens even if we could actually perform this operation. Suppose, for example, that I do survive as one of the resulting people. I would believe that I have survived. But I would know that the other resulting person falsely believes that he is me, and that he survived. Since I would know this, I could not trust my own belief. I might be the resulting person with the false belief. And, since we would both claim to be me, other people would have no reason to believe one of us rather than the other. Even if we performed this operation, we would therefore learn nothing.

Whatever happened to me, we could not discover what happened. This suggests a more radical answer to our question. It suggests that the Reductionist View is true. Perhaps there are not here different possibilities, each of which might be what happens, though we could never know which actually happens. Perhaps, when we know that each resulting person would have one half of my brain, and would be psychologically continuous with me, we know everything. What are we supposing when we suggest, for instance, that one of the resulting people might be me? What would make this the true answer?

I believe that there cannot be different possibilities, each of which might be the truth, unless we are separately existing entities, such as Cartesian Egos. If what I really am is one particular Ego, this explains how it could be true that one of the resulting people would be me. It could be true that it is in this person's brain and body that this particular Ego regained consciousness.

If we believe in Cartesian Egos, we might be reminded of Buridan's ass, which starved to death between two equally nourishing bales of hay. This ass had no reason to eat one of these bales of hay before eating the other. Being an overly‐rational beast it refused to make a choice for which there was no reason. In my example, there would be no reason why the particular (p.259) Ego that I am should wake up as one of the two resulting people. But this might just happen, in a random way, as is claimed for fundamental particles.

The more difficult question, for believers in Cartesian Egos, is whether I would survive at all. Since each of the resulting people would be psychologically continuous with me, there would be no evidence supporting either answer to this question. This argument retains its force, even if I am a Cartesian Ego.

As before, a Cartesian might object that I have misdescribed what would happen. He might claim that, if we carried out this operation, it would not in fact be true that both of the resulting people would be psychologically continuous with me. It might be true that one or other of these people was psychologically continuous with me. In either of these cases, this person would be me. It might instead be true that neither person was psychologically continuous with me. In this case, I would not survive. In each of these three cases, we would learn the truth.

Whether this is a good objection depends on what the relation is between our psychological features and the states of our brains. As I have said, we have conclusive evidence that the carrier of psychological continuity is not indivisible. In the actual cases in which hemispheres have been disconnected, this produced two series of thoughts and sensations. These two streams of consciousness were both psychologically continuous with the original stream. Psychological continuity has thus, in several actual cases, taken a dividing form. This fact refutes the objection just given. It justifies my claim that, in the imagined case of My Division, both of the resulting people would be psychologically continuous with me. Since this is so, the Cartesian View can be advanced here only in the more dubious version that does not connect the Ego with any observable or introspectible facts. Even if I am such an Ego, I could never know whether or not I had survived. For Cartesians, this case is a problem with no possible solution.

Suppose that, for the reasons given earlier, we reject the claim that each of us is really a Cartesian Ego. And we reject the claim that a person is any other kind of separately existing entity, apart from his brain and body, and various mental and physical events. How then should we answer the question about what happens when I divide? I distinguished four possibilities. When I discussed each possibility, there seemed to be strong objections to the claim that it would be what happens. If we believe that these are different possibilities, any of which might be what happens, the case is a problem for us too.

On the Reductionist View, the problem disappears. On this view, the claims that I have discussed do not describe different possibilities, any of which might be true, and one of which must be true. These claims are merely different descriptions of the same outcome. We know what this outcome is. (p.260) There will be two future people, each of whom will have the body of one of my brothers, and will be fully psychologically continuous with me, because he has half of my brain. Knowing this, we know everything. I may ask, ‘But shall I be one of these two people, or the other, or neither?’ But I should regard this as an empty question. Here is a similar question. In 1881 the French Socialist Party split. What happened? Did the French Socialist Party cease to exist, or did it continue to exist as one or other of the two new Parties? Given certain further details, this would be an empty question. Even if we have no answer to this question, we could know just what happened.

I must now distinguish two ways in which a question may be empty. About some questions we should claim both that they are empty, and that they have no answers. We could decide to give these questions answers. But it might be true that any possible answer would be arbitrary. If this is so, it would be pointless and might be misleading to give such an answer. This would be true of the question ‘Shall I survive?’ in the central cases in the Combined Spectrum. And it would be true in the central cases in the other Spectra, if I would not survive in the case at the far end.

There is another kind of case in which a question may be empty. In such a case this question has, in a sense, an answer. The question is empty because it does not describe different possibilities, any of which might be true, and one of which must be true. The question merely gives us different descriptions of the same outcome. We could know the full truth about this outcome without choosing one of these descriptions. But, if we do decide to give an answer to this empty question, one of these descriptions is better than the others. Since this is so, we can claim that this description is the answer to this question. And I claim that there is a best description of the case where I divide. The best description is that neither of the resulting people will be me.

Since this case does not involve different possibilities, the important question is not, ‘Which is the best description?’ The important question is: ‘What ought to matter to me? How ought I to regard the prospect of division? Should I regard it as like death, or as like survival?’ When we have answered this question, we can decide whether I have given the best description.

Before discussing what matters, I shall fulfil an earlier promise. One objection to the Psychological Criterion is that psychological continuity presupposes personal identity. I answered this objection, in the case of memory, by appealing to the wider concept of quasi‐memory. Jane quasi‐remembered having someone else's past experiences. My Division provides another example. Since at least one of the two resulting people will not be me, he can quasi‐remember living someone else's life.

I did not show that, in describing the other relations that are involved in psychological continuity, we need not presuppose personal identity. Now that I have described My Division, this can be easily shown. One other (p.261) direct relation is that which holds between an intention and the later action in which this intention is carried out. It may be a logical truth that we can intend to perform only our own actions. But we can use a new concept of quasi‐intention. One person could quasi‐intend to perform another person's actions. When this relation holds, it does not presuppose personal identity.

The case of division shows what this involves. I could quasi‐intend both that one resulting person roams the world, and that the other stays at home. What I quasi‐intend will be done, not by me, but by the two resulting people. Normally, if I intend that someone else should do something, I cannot get him to do it simply by forming this intention. But, if I was about to divide, it would be enough simply to form quasi‐intentions. Both of the resulting people would inherit these quasi‐intentions, and, unless they changed their inherited minds, they would carry them out. Since they might change their minds, I could not be sure that they would do what I quasi‐intended. But the same is true within my own life. Since I may change my own mind, I cannot be sure that I shall do what I now intend to do. But I have some ability to control my future by forming firm intentions. If I was about to divide, I would have just as much ability, by forming quasi‐intentions, to control the futures of the two resulting people.

Similar remarks apply to all of the other direct psychological connections, such as those involved in the continuity of character. All such connections hold between me and each of the resulting people. Since at least one of these people cannot be me, none of these connections presupposes personal identity.

# 90. What Matters When I Divide?

Why Our Identity Is not What Matters 90. What Matters When I Divide?

Some people would regard division as being as bad, or nearly as bad, as ordinary death. This reaction is irrational. We ought to regard division as being about as good as ordinary survival. As I have argued, the two ‘products’ of this operation would be two different people. Consider my relation to each of these people. Does this relation fail to contain some vital element that is contained in ordinary survival? It seems clear that it does not. I would survive if I stood in this very same relation to only one of the resulting people. It is a fact that someone can survive even if half his brain is destroyed. And on reflection it was clear that I would survive if my whole brain was successfully transplanted into my brother's body. It was therefore clear that I would survive if half my brain was destroyed, and the other half was successfully transplanted into my brother's body. In the case that we are now considering, my relation to each of the resulting people thus contains everything that would be needed for me to survive as that person. It cannot be the nature of my relation to each of the resulting people that, in this case, causes it to fail to be survival. Nothing is missing. What is wrong can only be the duplication.

Suppose that I accept this, but still regard division as being nearly as bad (p.262) as death. My reaction is now indefensible. I am like someone who, when told of a drug that could double his years of life, regards the taking of this drug as death. The only difference in the case of division is that the extra years are to run concurrently. This is an interesting difference; but it cannot mean that there are no years to run. We might say: ‘You will lose your identity. But there are different ways of doing this. Dying is one, dividing is another. To regard these as the same is to confuse two with zero. Double survival is not the same as ordinary survival. But this does not make it death. It is even less like death.’

The problem with double survival is that it does not fit the logic of identity. Like several Reductionists, I claim

Relation R is what matters. R is psychological connectedness and/or psychological continuity, with the right kind of cause.43

I also claim

In an account of what matters, the right kind of cause could be any cause.

Other Reductionists might require that R have a reliable cause, or have its normal cause. To postpone this disagreement, consider only cases where R would have its normal cause. In these cases, Reductionists would all accept the following claim. A future person will be me if he will be R‐related to me as I am now, and no different person will be R‐related to me. If there is no such different person, the fact that this future person will be me just consists in the fact that relation R holds between us. There is nothing more to personal identity than the holding of relation R. In nearly all of the actual cases, R takes a one‐one form. It holds between one presently existing person and one future person. When R takes a one‐one form, we can use the language of identity. We can claim that this future person will be this present person.

In the imagined case where I divide, R takes a branching form. But personal identity cannot take a branching form. I and the two resulting people cannot be one and the same person. Since I cannot be identical with two different people, and it would be arbitrary to call one of these people me, we can best describe the case by saying that neither will be me.

Which is the relation that is important? Is what matters personal identity, or relation R? In ordinary cases we need not decide which of these is what matters, since these relations coincide. In the case of My Division these relations do not coincide. We must therefore decide which of the two is what matters.

If we believe that we are separately existing entities, we could plausibly claim that identity is what matters. On this view, personal identity is a deep further fact. But we have sufficient evidence to reject this view. If we are Reductionists, we cannot plausibly claim that, of these two relations, it is identity that matters. On our view, the fact of personal identity just consists (p.263) in the holding of relation R, when it takes a non‐branching form. If personal identity just consists in this other relation, this other relation must be what matters.

It may be objected: ‘You are wrong to claim that there is nothing more to identity than relation R. As you have said, personal identity has one extra feature, not contained in relation R. Personal identity consists in R holding uniquely—holding between one present person and only one future person. Since there is something more to personal identity than to relation R, we can rationally claim that, of the two, it is identity which is what matters.’

In answering this objection, it will help to use some abbreviations. Call personal identity PI. When some relation holds uniquely, or in a one‐one form, call this fact U. The view that I accept can be stated with this formula:

$Display mathematics$

Most of us are convinced that PI matters, or has value. Assume that R may also have value. There are then four possibilities:

1. (1) R without U has no value.

2. (2) U enhances the value of R, but R has value even without U.

3. (3) U makes no difference to the value of R.

4. (4) U reduces the value of R (but not enough to eliminate this value, since R + U = PI, which has value).

Can the presence or absence of U make a great difference to the value of R? As I shall argue, this is not plausible. If I will be R‐related to some future person, the presence or absence of U makes no difference to the intrinsic nature of my relation to this person. And what matters most must be the intrinsic nature of this relation.

Since this is so, R without U would still have at least most of its value. Adding U makes R = PI. If adding U does not greatly increase the value of R, R must be what fundamentally matters, and PI mostly matters just because of the presence of R. If U makes no difference to the value of R, PI matters only because of the presence of R. Since U can be plausibly claimed to make a small difference, PI may, compared with R, have some extra value. But this value would be much less than the intrinsic value of R. The value of PI is much less than the value that R would have in the absence of PI, when U fails to hold.

If it was put forward on its own, it would be difficult to accept the view that personal identity is not what matters. But I believe that, when we consider the case of division, this difficulty disappears. When we see why neither resulting person will be me, I believe that, on reflection, we can also see that this does not matter, or matters only a little.

(p.264) The case of division supports part of the Reductionist View: the claim that our identity is not what matters. But this case does not support another Reductionist claim: that our identity can be indeterminate. If we abandon the view that identity is what matters, we can claim that there is an answer here to my question. Neither of the resulting people will be me. I am about to die. While we believed that identity is what matters, this claim implied, implausibly, that I ought to regard My Division as being nearly as bad as ordinary death. But the implausibility disappears if we claim instead that this way of dying is about as good as ordinary survival.

There is still room for minor disagreements. Though R is what fundamentally matters, U can make a slight difference. I might regard my division as being somewhat better than ordinary survival, or as being somewhat worse.

Why might I think it somewhat worse? I might claim that the relation between me and each of the resulting people is not quite the relation that matters in ordinary survival. This is not because something is missing, but because division brings too much. I may think that each of the resulting people will, in one respect, have a life that is worse than mine. Each will have to live in a world where there is someone else who, at least to start with, is exactly like himself. This may be unpleasantly uncanny. And it will raise practical problems. Suppose that what I most want is to write a certain book. This would be what each of the resulting people would most want to do. But it would be pointless for both to write this book. It would be pointless for both to do what they most want to do.

Consider next the relations between the resulting people and the woman I love. I can assume that, since she loves me, she will love them both. But she could not give to both the undivided attention that we now give to each other.

In these and other ways the lives of the resulting people may not be quite as good as mine. This might justify my regarding division as being not quite as good as ordinary survival. But it could not justify regarding division as being much less good, or as being as bad as death. And we should note that this reasoning ignores the fact that these two lives, taken together, would be twice as long as the rest of mine.

Instead of regarding division as being somewhat worse than ordinary survival, I might regard it as being better. The simplest reason would be the one just given: the doubling of the years to be lived. I might have more particular reasons. Thus there might be two life‐long careers both of which I strongly want to pursue. I might strongly want both to be a novelist and to be a philosopher. If I divide, each of the resulting people could pursue one of these careers. And each would be glad if the other succeeds. Just as we can take pride and joy in the achievements of our children, each of the resulting people would take pride and joy in the other's achievements.

(p.265) If I have two strong but incompatible ambitions, division provides a way of fulfilling both, in a way that would gladden each resulting person. This is one way in which division could be better than ordinary survival. But there are other problems that division could not wholly solve. Suppose that I am torn between an unpleasant duty and a seductive desire. I could not wholly solve this problem by quasi‐intending one of the resulting people to do my duty, and quasi‐intending the other to do what I desire. The resulting person whom I quasi‐intend to do my duty would himself be torn between duty and desire. Why should he be the one to do my unpleasant duty? We can foresee trouble here. My duty might get done if the seductive desire could not be fulfilled by more than one person. It might be the desire to elope with someone who wants only one companion. The two resulting people must then compete to be this one companion. The one who fails in this competition might then, grudgingly, do my duty. My problem would be solved, though in a less attractive way.

These remarks will seem absurd to those who have not yet been convinced that the Reductionist View is true, or that identity is not what matters. Such a person might say: ‘If I shall not be either of the resulting people, division could not fulfil my ambitions. Even if one of the resulting people is a successful novelist, and the other a successful philosopher, this fulfils neither of my ambitions. If one of my ambitions is to be a successful novelist, my ambition is that I be a successful novelist. This ambition will not be fulfilled if I cease to exist and someone else is a successful novelist. And this is what would happen if I shall be neither of the resulting people.’

This objection assumes that there is a real question whether I shall be one of the resulting people, or the other, or neither. It is natural to assume that these are three different possibilities, any of which might be what happens. But as I have argued, unless I am a separately existing entity, such as a Cartesian Ego, these cannot be three different possibilities. There is nothing that could make it true that any of the three might be what really happens. (This is compatible with my claim that there is a best description of this case: that I shall be neither resulting person. This does not commit me to the view that there are different possibilities. This would be so only if one of the other descriptions might have been the truth—which I deny.)

We could give a different description. We could say that I shall be the resulting person who becomes a successful novelist. But it would be a mistake to think that my ambition would be fulfilled if and only if we called this resulting person me. How we choose to describe this case has no rational or moral significance.

I shall now review what I have claimed. When I discussed the Psychological, Physical, and Combined Spectra, I argued that our identity can be indeterminate. This is not the natural view. We are inclined to believe that, to the question ‘Am I about to die?’, there must always be an answer, which must be either Yes or No. We are inclined to believe that our identity must be (p.266) determinate. I argued that this cannot be true unless we are separately existing entities, such as Cartesian Egos. We cannot both deny that a person is such an entity, and insist that the continued existence of a person has the same special features that Cartesians attribute to the existence of the Ego. I conceded that we might have been such entities. But there is much evidence against this view.

If we deny that we are separately existing entities, we must, I have claimed, become Reductionists. One Reductionist claim is that we can imagine cases where the question ‘Am I about to die?’ has no answer, and is empty. This seems the least implausible view about the central cases in the Combined Spectrum. Another Reductionist claim is that personal identity is not what matters. This seems the least implausible view about the case of My Division. Of these two Reductionist claims, the second is more important, since it applies to our own lives.

If we accept the Reductionist View, we have further questions to answer about what matters. These are questions about the rational and moral significance of certain facts. But, on the Reductionist View, the so‐called ‘problem cases’ cease to raise problems about what happens. Even when we have no answer to a question about personal identity, we can know everything about what happens.

Have I overlooked some view? I have claimed that, if we reject the view that we are separately existing entities, we should accept some version of the Reductionist View. But certain writers defend views that are not obviously versions of either of these views. I shall therefore discuss what these writers claim.

# 91. Why There is No Criterion of Identity That Can Meet Two Plausible Requirements

Why Our Identity Is not What Matters 91. Why No Criterion of Identity Can Meet Two Requirements

Besides the argument discussed in Section 83, Williams advances another argument against the Psychological Criterion. It may again help if I state, in advance, what I believe this argument to show. Williams claims that the criterion of personal identity must meet two requirements. I shall claim that no plausible criterion of identity can meet both requirements. In contrast, on the Reductionist View, the analogous requirements can be met. The argument therefore gives us further grounds for accepting this view. But Williams's argument does not assume the Reductionist View. In discussing the argument, I shall therefore briefly set aside this view. It can wait in the wings, to reappear when the action demands it.

Williams's argument develops a remark of Reid's, against Locke's claim that whoever ‘has the consciousness of present and past actions is the same person to whom they belong’. This implies, as Reid writes, ‘that if the same consciousness can be transferred from one intelligent being to another . . . (p.267) then two or twenty intelligent beings may be the same person’.44

Williams argues as follows. Identity is logically a one‐one relation. It is logically impossible for one person to be identical to more than one person. I cannot be one and the same person as two different people. As we have seen, psychological continuity is not logically a one‐one relation. Two different future people could both be psychologically continuous with me. Since these different people cannot both be me, psychological continuity cannot be the criterion of identity. Williams then claims that, to be acceptable, a criterion of identity must itself be logically a one‐one relation. It must be a relation which could not possibly hold between one person and two future people. He therefore claims that the criterion of identity cannot be psychological continuity.45

Some reply that this criterion might appeal to non‐branching psychological continuity. This is the version of this criterion that I have discussed. On what I call the Psychological Criterion, a future person will be me if he will be R‐related to me, and there is no other person who will be R‐related to me. Since this version of this criterion is logically a one‐one relation, it has been claimed that it answers Williams's objection.46

Williams rejects this answer. He claims

Requirement (1): Whether a future person will be me must depend only on the intrinsic features of the relation between us. It cannot depend on what happens to other people.

Requirement (2): Since personal identity has great significance, whether identity holds cannot depend on a trivial fact.47

These requirements are both plausible. And neither requirement is met by non‐branching psychological continuity. Williams therefore rejects this version of the Psychological Criterion.

This objection may seem too abstract to be convincing. Its force can be shown if I vary the imagined story with which I began. Consider Simple Teletransportation where the Scanner destroys my brain and body. After my blueprint is beamed to Mars, the Replicator makes a perfect organic copy. My Replica on Mars will think that he is me, and he will be in every way psychologically continuous with me.

Suppose that we accept the Psychological Criterion which appeals to relation R when it holds in a one‐one form. And suppose that we accept the Wide version, which allows R to have any reliable cause. This criterion implies that my Replica on Mars will be me. But we might learn that my blueprint is also being beamed to Io, one of the satellites of Jupiter. We must then claim that it will be me who wakes up on Mars, and that I shall continue to exist if my blueprint is ignored by the scientists on Io. But if the scientists on Io later make another Replica of me, when that Replica wakes up I shall cease to exist. Though the people around me on Mars will not (p.268) notice any change, at that moment a new person will come into existence in my brain and body. Williams would object that, if I do wake up on Mars, whether I continue to exist there cannot depend, as we claim, on what happens to someone else millions of miles away near Jupiter. Our claim violates Requirement (1).

As I have argued, what fundamentally matters is whether I shall be R‐related to at least one future person. It is relatively trivial whether I shall also be R‐related to some other person. On this version of the Psychological Criterion, whether I shall be identical to some future person depends upon this relatively trivial fact. This violates Requirement (2).

Williams would add these remarks. Once we see that Teletransportation could produce many Replicas of me, who would be different people from each other, we should deny that I would in fact wake up on Mars even if they make only a single Replica. If they made two Replicas, these could not both be me. If they could not both be me, but they are produced in just the same way, we ought to conclude that neither would be me. But my relation to one of the Replicas is intrinsically the same whether or not they make the other. Since identity must depend on the intrinsic features of a relation, I would be neither Replica even if they did not make the other.48

Williams takes this argument to support a Non‐Reductionist version of the Physical Criterion. (This version is Non‐Reductionist because it assumes that personal identity is a further fact that requires, rather than consists in, physical continuity.) As Williams admits, a similar argument can challenge this view. He rejects the Psychological Criterion because it appeals to a relation that can take a branching form, holding between one person and two or more future people, and it therefore fails to meet his two requirements. He then considers the objection that his version of the Physical Criterion also fails to meet his requirements. Physical continuity could take a branching form. As he writes, ‘It is possible to imagine a man splitting, amoeba‐like, into two simulacra of himself.’49

Williams gives two answers to this objection. Suppose we believe that my brain and body are physically continuous with the brain and body of the person whom my parents cared for as their second child. We wish to know whether this physical continuity took an abnormal, branching form. If we knew the full history of this physically continuous brain and body, this would ‘inevitably reveal’ whether there had been such a case of amoeba‐like division. The comparable claim is not true in the case of psychological continuity. We might know the full history of the psychological continuity between me on Earth and my Replica on Mars, yet fail to know that I have another Replica on Io. Branching is a problem for both the Physical and the Psychological Criterion. But the problem is less serious for the Physical Criterion, since it would be in principle easier to know when the problem arises.

Williams also claims that, when a physical object divides, this is an (p.269) intrinsic feature of its spatio‐temporal continuity. In contrast, when two people are psychologically continuous with one earlier person, this fact is not an intrinsic feature of either of these relations. Unlike the Psychological Criterion, the Physical Criterion meets Requirement (1).

My imagined division provides objections to the Physical Criterion. I revised this criterion in two ways. I first considered the case where my brain is transplanted into the body of my identical twin. On reflection it was clear that I am here the surviving recipient, not the dead donor. If my brain is given a new body, this is just the limiting case of receiving a new heart, new lungs, and so on. The Physical Criterion ought to appeal only to the continuity of my brain. I then appealed to the fact that many people have survived with one of their hemispheres destroyed. Since it is clear that these people survived, the Physical Criterion ought to appeal to the continuity, not of the whole brain, but of enough of the brain to support conscious life.

Such continuity is not logically a one‐one relation. In the imagined case where I divide, each of the two resulting people has enough of my brain to support conscious life. And we cannot dismiss this case with the claim that it could never happen. Its most troubling feature, the division of consciousness, has already happened. It may remain impossible to divide the lower brain. But this is a mere technical impossibility. In the same way, Teletransportation may never be possible. But such impossibility does not weaken Williams's argument against the Wide Psychological Criterion. And if he appeals to such cases in that argument, he cannot dismiss the imagined case of my complete division.

Williams's argument implies that, in this case, I shall cease to exist, and both of the resulting people would be new people. He must therefore revise the Physical Criterion, so that it takes a non‐branching form. Someone might appeal to the version that I described. This is

The Physical Criterion: If there will be a future person with enough of my brain to be the brain of a living person, this person will be me, unless there will also be someone else with enough of my brain.

Williams would reject this Criterion, since it violates both of his Requirements.

It is again worth giving an example. Suppose that My Division proceeds as follows. I have two fatally brain‐damaged brothers, Jack and Bill. A surgeon first removes and divides my brain. The halves are then taken to different wings of the hospital, where they will be transplanted into the bodies of my two brothers. If we appeal to the Physical Criterion, we must claim the following. Suppose that one half of my brain is successfully transplanted into Jack's body. Before the other half can be transplanted, it is dropped onto a concrete floor. If this is what happens, I shall wake up in Jack's body. But if the other half was successfully transplanted, I would wake up in neither body.

(p.270) These claims violate Requirement (1). Whether I am the person in Jack's body ought to depend only on the intrinsic features of the relation between me and this person. It cannot plausibly be thought to depend on what happens in the other wing of the hospital. What happens elsewhere seems to be as irrelevant as whether the scientists on Io make a Replica of me. Whatever happens to Bill, and to the other half of my brain, my relation to the person in Jack's body must be the same. This claim is denied by the Physical Criterion. And, compared with the importance of the fact that half my brain will survive in Jack's body, what happens to the other half is, for me, relatively trivial. This criterion therefore also violates Requirement (2).

Williams might suggest

The New Physical Criterion: A future person will be me if and only if this person is both living and has more than half my brain.50

It is an intrinsic feature of this relation that it can take only a one‐one form. It is logically impossible for two future people both to have more than half my brain. This criterion therefore meets Requirement (1).

It fails, however, to meet the other requirement. I could be fully psychologically continuous with some future person both when this person has half of my brain and when this person has slightly more than half. And, for those who believe that what matters is physical continuity, the difference between these cases must be trivial. The second involves the continuity of just a few more cells. It is a trivial fact whether some future person has half my brain, or slightly more than half. The New Physical Criterion therefore violates Requirement (2).

There is another objection to this criterion. Someone might suffer injuries which cause more than half his brain to cease to function. Though such a person would be paralysed in more than half his body, and might need to be placed in a heart‐lung machine, his mental life could be unaffected. Less than half a brain would be enough to provide full psychological continuity. We would naturally believe that such a person survives his injury. But, on the New Physical Criterion, we must claim that such a person ceases to exist. The person in his body is someone else, a new person who is merely exactly like him. This is hard to believe. It is a second strong objection to this criterion.

In all of its possible versions, the Physical Criterion faces strong objections. And there are similar objections to the Psychological Criterion. Williams's requirements are both plausible. We have found that no plausible criterion of identity can meet both requirements. (If we were separately existing entities, like Cartesian Egos, our criterion might meet these requirements; but we have sufficient reasons to reject this view.)

(p.271) Return now to the Reductionist View. Reconsider the case where half my brain is successfully transplanted into Jack's body. What is my relation to the person waking up in Jack's body? This relation is psychological continuity, with its normal cause, the continued existence of enough of my brain. There is also very close physical similarity. As a Reductionist, I claim that my relation to the person in Jack's body contains what fundamentally matters. This claim stands whatever happens to other people elsewhere. With one revision, my view meets Williams's first requirement. He claims that whether I shall be some future person ought to depend only on my relation to this future person. I make a similar claim. Instead of asking whether I shall be some future person, I ask whether my relation to this person contains what matters. Like Williams, I can claim that the answer must depend only on the intrinsic features of my relation to this future person.

The Reductionist View can meet this revised version of Requirement (1). Suppose that the other operation succeeds. Someone wakes up in Bill's body. On my view, this does not change the relation between me and the person in Jack's body. And it makes at most a little difference to the importance of this relation. This relation still contains what fundamentally matters. Since this relation now holds in a branching form, we are forced to change its name. We cannot call each branch of this relation personal identity. But this change in the relation's name has no significance.

This Reductionist View also meets the analogue of Requirement (2). Judgements of personal identity have great importance. Williams therefore claims that we should not make one such judgement and deny another without an important difference in our grounds. On this Reductionist View, we should take the importance that we give to a judgement of identity, and we should give this importance to a different relation. On this view, what is important is relation R: psychological connectedness and/or continuity, with the right kind of cause. Unlike identity, this relation cannot fail to hold because of a trivial difference in the facts. If this relation fails to hold, there is a deep difference in the facts. This meets Requirement (2).

In the case where I divide, though my relation to each of the resulting people cannot be called identity, it contains what fundamentally matters. When we deny identity here, we need not be denying an important judgement. Since my relation to each of the resulting people is about as good as if it were identity, it may carry most of the ordinary implications of identity. Thus it might be claimed that, even when the person in Jack's body cannot be called me, because the other transplant succeeds, he can just as much deserve punishment or reward for what I have done. So can the person in Bill's body. As Wiggins writes: ‘a malefactor could scarcely evade responsibility by contriving his own fission’.51

There are questions to be answered here. If the malefactor is sentenced to twenty years in prison, should each resulting person serve twenty years, or (p.272) only ten? I discuss some of these questions in Chapter 15. These questions do not cast doubt on the general claim I have made. If we accept the Reductionist View, it is R and not identity which is what matters.

It may be thought that, if this is so, we ought to give to R the importance that we now give to personal identity. This does not follow. If we believe that personal identity has great importance, this may be because we believe the Non‐Reductionist View. If we change our view, and become Reductionists, we may also change our view about the importance of personal identity. We may accept that relation R has nearly all of the importance that, on the Reductionist View, personal identity has. And we may accept that, on this view, what fundamentally matters is not personal identity but R. But we may believe that both these relations have much less importance than personal identity would have if the Non‐Reductionist View was true. I discuss this belief in Chapters 14 and 15.

This belief does not affect my claims about Williams's requirements. If we assume that identity is what matters, we cannot meet these requirements. Since we should reject the Non‐Reductionist View, our criterion of identity should be either the Physical or the Psychological Criterion. And, as I have argued, there is no plausible version of either criterion that meets both of Williams's requirements.

I add these remarks. Now that we have seen that identity is not what matters, we should not try to revise or extend our criterion of identity, so that it coincides more often with what matters. On any natural understanding of personal identity, such a coincidence could be only partial, as the case of division shows. And revising our criterion may misleadingly suggest that identity is what matters.

Williams gives one other ground for requiring that a criterion of identity be logically one‐one, and in a way that is not arbitrary. ‘Unless there is some such requirement, I cannot see how one is to preserve and explain the evident truth that the concepts of identity and of exact similarity are different concepts.’52

The Reductionist View preserves and explains this truth. I have described cases where there are two people who are exactly similar but are not numerically identical. This may be true in the Branch‐Line Case, in which I talk to my Replica. We therefore understand the question, ‘Is he one and the same person as me, or is he merely another person, who is exactly similar?’ I have claimed that, in some cases, such as those in the middle of the Physical Spectrum, there is not a real difference between the resulting person's being me, and his being someone else, who is merely exactly like me. The Reductionist view does imply that, in some cases, there is not a real difference between numerical identity and exact similarity. But since it recognises other cases where this is a real difference, it preserves and explains the truth that these are different concepts.

(p.273) I discussed Williams's claims to see if they provide some third view, different from both the Reductionist View and the view that we are separately existing entities. I conclude that these claims do not provide such a third view. They provide further grounds for accepting the Reductionist View. Williams's requirements are both plausible. If we believe that identity is what matters, we cannot meet these requirements. But if we accept the Reductionist View, and appeal to Relation R, we can meet the analogous requirements.

# 92. Wittgenstein and Buddha

Wittgenstein would have rejected the Reductionist View. He believed that our concepts depend on the holding of certain facts, and that we should not consider imaginary cases where these facts no longer hold. The arguments for the Reductionist View appeal to such cases.

This disagreement is only partial. Most people have beliefs about these imaginary cases. As I have argued, these beliefs imply that we are separately existing entities, distinct from our brains and bodies, and entities whose existence must be all‐or‐nothing. A Reductionist's main claim is that we should reject these beliefs. Wittgenstein would have agreed. Given this agreement about this claim, I need not discuss Wittgenstein's view, or some other similar views, such as that advanced by Wiggins.53

With two exceptions that I shall soon mention, I believe that I have now considered those views that, in this debate, need to be considered. I may be unaware of some other published view. And I have not considered views held in different ages, or civilizations. This fact suggests a disturbing possibility. I believe that my claims apply to all people, at all times. It would be disturbing to discover that they are merely part of one line of thought, in the culture of Modern Europe and America.

Fortunately, this is not true. I claim that, when we ask what persons are, and how they continue to exist, the fundamental question is a choice between two views. On one view, we are separately existing entities, distinct from our brain and bodies and our experiences, and entities whose existence must be all‐or‐nothing. The other view is the Reductionist View. And I claim that, of these, the second view is true. As Appendix J shows, Buddha would have agreed. The Reductionist View is not merely part of one cultural tradition. It may be, as I have claimed, the true view about all people at all times.

# 93. Am I Essentially My Brain?

Nagel suggests a view of a kind that I have not discussed. He suggests that what I really am is whatever is the cause of my psychological continuity. Given what we now know, what I really am is my brain. On this view, moreover, I am essentially my brain. I cannot decide to take a different view about myself.

(p.274) Nagel supports this view in three ways. He gives two arguments, which I try to answer in Appendix D. He also claims that his view is intuitively plausible. As he writes, his brain.

seems to me to be something without which I could not survive—so that if a physically distinct replica of me were produced who was psychologically continuous with me though my brain had been destroyed, it would not be me and its survival would not be as good as my survival.

Nagel is here considering a case like that of Teletransportation. The Scanning Replicator could have uses here on Earth. I could use it as a safer way to cross Manhattan, or as the cure if, while I walk across Manhattan, I am fatally stabbed. As a precaution, before each walk, I could have a new blueprint stored.

Nagel suggests that Teletransportation is not merely not as good as ordinary survival, but is nearly as bad as death. As he writes, after describing his imagined case,

I will not survive the night . . . the replica will not be me. Trying to summon my courage, I prepare for the end.

This suggests that, on Nagel's view, personal identity is what matters. I admit that, in a case like Teletransportation, many people would accept Nagel's view. They would believe that what matters is the survival of their brains. In Appendix D I describe two cases where this is harder to believe.

Since Nagel's view is, in some cases, intuitively plausible, and Appendix D may fail to answer Nagel's arguments, I shall give, in Section 98, a different kind of answer to this and similar views.

There is one other view that I should consider. I explain in Appendix E how, despite an apparent disagreement, Nozick's view is a version of Reductionism.

# 94. Is the True View Believable?

Why Our Identity Is not What Matters 94. Is the True View Believable?

Nagel once claimed that, even if the Reductionist View is true, it is psychologically impossible for us to believe this. I shall therefore briefly review my arguments given above. I shall then ask whether I can honestly claim to believe my conclusions. If I can, I shall assume that I am not unique. There would be at least some other people who can believe the truth.

I shall first qualify my claim that I have described the true view. It is hard to explain accurately what a Reductionist claims. And it is hard to explain accurately what is involved in identity over time. It is likely that, in describing a Reductionist view about identity, I have made mistakes.

Such mistakes may not wholly undermine my arguments. Wittgenstein suggested this analogy. Suppose that I am rearranging the books in a library. At the start of this rearrangement, I place two books together on a (p.275) particular shelf, because these books ought to be together. I may know that, at the end of this rearrangement, these two books will be on a different shelf. But it is still worth putting them together now. If they ought to be together, they will still be together after this rearrangement.

I claim that a person is not like a Cartesian Ego, a being whose existence must be all‐or‐nothing. A person is like a nation. In the true account of identity over time, these two kinds of entities go together. They are like the two books that I start by placing on a shelf. In my claims about Reductionism and identity, I may have made mistakes. This would be like the fact that the two books should go on a different shelf. But my main claim is that persons are like nations, not Cartesian Egos. If this claim is true, it would not be undermined by my mistakes. In the account that makes no mistakes, persons and nations would still go together. The account of their identity over time would, in its essential features, be similar.

I distinguished two views about the nature of persons. On the Non‐Reductionist View, a person is a separately existing entity, distinct from his brain and body, and his experiences. On the best‐known version of this view, a person is a Cartesian Ego. On the Reductionist View that I defend, persons exist. And a person is distinct from his brain and body, and his experiences. But persons are not separately existing entities. The existence of a person, during any period, just consists in the existence of his brain and body, and the thinking of his thoughts, and the doing of his deeds, and the occurrence of many other physical and mental events.

Since these views disagree about the nature of persons, they also disagree about the nature of personal identity over time. On the Reductionist View, personal identity just involves physical and psychological continuity. As I argued, both of these can be described in an impersonal way. These two kinds of continuity can be described without claiming that experiences are had by a person. A Reductionist also claims that personal identity is not what matters. Personal identity just involves certain kinds of connectedness and continuity, when these hold in a one‐one form. These relations are what matter.

On the Non‐Reductionist View, personal identity is what matters. And it does not just involve physical and psychological continuity. It is a separate further fact, which must, in every case, either hold completely, or not at all. Psychological unity is explained by ownership. The unity of consciousness at any time is explained by the fact that several experiences are being had by a person. And the unity of a person's life is explained in the same way. These several claims must, I have argued, stand or fall together.

I conceded that the Non‐Reductionist View might have been true. There might for example have been evidence supporting the belief in reincarnation. But there is in fact no good evidence for this view, and much evidence against it.

(p.276) Some of the evidence is provided by the actual cases of divided minds. Because their hemispheres have been disconnected, several people have two streams of consciousness, in each of which they are unaware of the other. We might claim that, in such a case, there are two different people in the same body. This treats such cases as being like the imagined case where I divide, which I review below. Our alternative is to claim, about these actual cases, that there is a single person with two streams of consciousness.

If we make this claim, how can we explain the unity of consciousness in each stream? We cannot explain this unity by claiming that the various different experiences in each stream are being had by the same person, or subject of experiences. This describes the two streams as if they were one. If we believe that the unity of consciousness must be explained by ascribing different experiences to a particular subject, we must claim that in these cases, though there is only a single person, there are two subjects of experiences. We must therefore claim that there can be, in a person's life, subjects of experiences that are not persons. It is hard to believe that there really are such things. These cases are better explained by the Reductionist Psychological Criterion. This claims that, at any time, there is one state of awareness of the experiences in one stream of consciousness, and another state of awareness of the experiences in the other stream.

Though they raise this problem for the Non‐Reductionist View, these cases of divided minds are only a small part of the evidence against this view. There is no evidence that the carrier of psychological continuity is something whose existence, like that of a Cartesian Ego, must be all‐or‐nothing. And there is much evidence that the carrier of this continuity is the brain. There is much evidence that our psychological features depend upon states and events in our brains. A brain's continued existence need not be all‐or‐nothing. Physical connectedness can be a matter of degree. And there are countless actual cases in which psychological connectedness holds only in certain ways, or to some reduced degree.

We have sufficient evidence to reject the Non‐Reductionist View. The Reductionist View is, I claim, the only alternative. I considered possible third views, and found none that was both non‐Reductionist and a view that we had sufficient reasons to accept. More exactly, though these other views differ in other ways, the plausible views do not deny a Reductionist's central claim. They agree that we are not separately existing entities, distinct from our brains and bodies and our experiences, whose existence must be all‐or‐nothing.

Besides making these claims about the facts, I made claims about our beliefs. We learn that we have these beliefs when we consider certain imaginary cases.

One of these is the case in which, by tampering with my brain, a surgeon gradually removes all of my psychological continuity. I described three other ranges of cases. In the Psychological and Physical Spectra there would be, between me and some future person, all of the possible degrees of either (p.277) psychological or physical connectedness. In the Combined Spectrum, there would be all of the possible degrees of both kinds of connectedness.

Like most of us, I am strongly inclined to believe that any future person must be either me or someone else. And I am inclined to believe that there is always a deep difference between these two outcomes. Since I am not a separately existing entity, these beliefs cannot be true. This is best shown by considering the Combined Spectrum. In the case at the near end, where nothing would be done to me, the resulting person would certainly be me. In the case at the far end, where there would be no connections between me and the resulting person, this person would certainly be someone else. If any future person must be either me or someone else, there must be a line in this range of cases up to which the resulting person would be me, and beyond which he would be someone else. If there is always a deep difference between some person's being me and his being someone else, there must be a deep difference between two of the cases in this Spectrum. There must be such a deep difference, though we could never discover where this difference comes. These claims are false. There is no deep difference between any neighbouring cases in this range. The only differences are that, in one of the cases, the surgeons would replace a few more cells, and would make one more small psychological change.

When I consider this range of cases, I am forced to abandon at least one of the two beliefs mentioned above. I cannot continue to believe both that any future person must be either me or someone else, and that there is always a deep difference between these two outcomes.

I am also forced to accept another part of the Reductionist View. Suppose that I am about to undergo one of the operations in the middle of this spectrum. I know that, between me and the resulting person, there will be certain kinds and amounts of physical and psychological connectedness. On the Reductionist View, in knowing these facts I know the full truth about what will happen. When I am about to lose consciousness, I may ask, ‘Am I about to die? Or shall I be the resulting person?’ And I am inclined to believe that these are always two different possibilities, one of which must be the truth. On the Reductionist View, this is here an empty question. There is sometimes a real difference between some future person's being me, and his being someone else. But there is no such real difference in the cases in the middle of the Combined Spectrum. What could the difference be? What could make it true either that the resulting person would be me, or that he would be someone else? Since I am not a separately existing entity, there is nothing that could make these different possibilities, either of which might be true. In these cases, we could say that the resulting person will be me, or we could say that I shall die and he will be someone else. But these are not here different outcomes. They are merely different descriptions of the same outcome.

To illustrate these claims, I repeated Hume's comparison. Persons are like nations, clubs, or political parties. If we are considering these other entities, (p.278) most of us accept a Reductionist view. Remember the political party which split, and became two rival parties. We can ask, ‘Did the original party cease to exist, or did it continue to exist as one or other of the resulting parties?’ But we do not believe that this is a real question, about different possibilities, one of which must be what happened. This question is empty. Even if we have no answer to this question, we could know the full truth about what happened.

Since we accept Reductionist views about political parties, or clubs, or nations, we understand, in a rough way, what is being claimed by the Reductionist View about persons. But most of us are strongly inclined to reject this view. We are strongly inclined to believe that there must always be a difference between some future person's being me, and his being someone else. Considering my Combined Spectrum may not be enough to persuade us to become Reductionists. I therefore gave further arguments.

One argument appealed to the imagined case where I divide. The division of one stream of consciousness might be claimed to be deeply impossible. But what happens must be possible: and in the lives of several people this has happened. My imagined Division is a natural extension of these actual cases.

In this imagined case, each half of my brain is successfully transplanted into another body. What happens to me? Unless we grotesquely distort the concept of a person, the only possible answers are that I shall be one of the resulting people, or the other, or neither. If we believe that identity is what matters, each of these answers is hard to accept. Given the exact similarity of the two resulting people, it is hard to believe that I shall be one of these two people. If I shall be neither of these people, and identity is what matters, I ought to regard division as equivalent to death. But this is also hard to believe. My relation to each resulting person contains everything that would be needed for survival. This relation cannot be called identity because and only because it holds between me and two future people. In ordinary death, this relation holds between me and no future person. Though double survival cannot be described in the language of identity, it is not equivalent to death. Two does not equal zero.

This imagined case supports another part of the Reductionist View. Not only is each of the possible answers hard to believe. It is hard to see how the case could involve different possibilities, any of which might be the truth. If I am not a Cartesian Ego, what could make it true that I would be one of the two resulting people, or the other? If these are different possibilities, in what could the difference consist? There seems to be no answer to this question. Each of the resulting people will have half my brain, and will be fully psychologically continuous with me. We seem forced to conclude that this is a full description of the case. We understand the question, ‘Shall I be one of these two people, or the other, or neither?’ But this is another empty question. These are not here different possibilities, one of which must be true. (p.279) These are merely different descriptions of the same outcome.

The best description is that I shall be neither resulting person. But this does not imply that I should regard division as nearly as bad as death. As I argued, I should regard it as about as good as ordinary survival. For some people, it would be slightly better; for others, it would be slightly worse. Since I cannot be one and the same person as the two resulting people, but my relation to each of these people contains what fundamentally matters in ordinary survival, the case shows that identity is not what matters. What matters is Relation R: psychological connectedness and/or psychological continuity, with the right kind of cause.

I have now reviewed the main arguments for the Reductionist View. Do I find it impossible to believe this View?

What I find is this. I can believe this view at the intellectual or reflective level. I am convinced by the arguments in favour of this view. But I think it likely that, at some other level, I shall always have doubts.

My belief is firmest when I am considering some of these imagined cases. I am convinced that, if I divided, it would be an empty question whether I shall be one, or the other, or neither of the resulting people. I believe that there is nothing that could make these different possibilities, any of which might be what would really happen. And I am convinced that, in the central cases of the Third Spectrum, it is an empty question whether the resulting person would be me.

When I consider certain other cases, my conviction is less firm. One example is Teletransportation. I imagine that I am in the cubicle, about to press the green button. I might suddenly have doubts. I might be tempted to change my mind, and pay the larger fare of a space‐ship journey.

I suspect that reviewing my arguments would never wholly remove my doubts. At the reflective or intellectual level, I would remain convinced that the Reductionist View is true. But at some lower level I would still be inclined to believe that there must always be a real difference between some future person's being me, and his being someone else. Something similar is true when I look through a window at the top of a sky‐scraper. I know that I am in no danger. But, looking down from this dizzying height, I am afraid. I would have a similar irrational fear if I was about to press the green button.

It may help to add these remarks. On the Reductionist View, my continued existence just involves physical and psychological continuity. On the Non‐Reductionist View, it involves a further fact. It is natural to believe in this further fact, and to believe that, compared with the continuities, it is a deep fact, and is the fact that really matters. When I fear that, in Teletransportation, I shall not get to Mars, my fear is that the abnormal cause may fail to produce this further fact. As I have argued, there is no such fact. What I fear will not happen, never happens. I want the person on (p.280) Mars to be me in a specially intimate way in which no future person will ever be me. My continued existence never involves this deep further fact. What I fear will be missing is always missing. Even a space‐ship journey would not produce the further fact in which I am inclined to believe.

When I come to see that my continued existence does not involve this further fact, I lose my reason for preferring a space‐ship journey. But, judged from the stand‐point of my earlier belief, this is not because Teletransportation is about as good as ordinary survival. It is because ordinary survival is about as bad as, or little better than, Teletransportation. Ordinary survival is about as bad as being destroyed and Replicated.

By rehearsing arguments like these, I might do enough to reduce my fear. I might be able to bring myself to press the green button. But I expect that I would never completely lose my intuitive belief in the Non‐Reductionist View. It is hard to be serenely confident in my Reductionist conclusions. It is hard to believe that personal identity is not what matters. If tomorrow someone will be in agony, it is hard to believe that it could be an empty question whether this agony will be felt by me. And it is hard to believe that, if I am about to lose consciousness, there might be no answer to the question ‘Am I about to die?’

Nagel once claimed that it is psychologically impossible to believe the Reductionist View. Buddha claimed that, though this is very hard, it is possible. I find Buddha's claim to be true. After reviewing my arguments, I find that, at the reflective or intellectual level, though it is very hard to believe the Reductionist View, this is possible. My remaining doubts or fears seem to me irrational. Since I can believe this view, I assume that others can do so too. We can believe the truth about ourselves.

## Notes:

(33) SPERRY, p. 299.

(34) NAGEL (5), reprinted in NAGEL (4) p. 152.

(35) NAGEL, op. cit., p. 153.

(36) MADELL, p. 137, suggests that what makes my experiences mine is not that they are had by a particular subject of experiences, me, but that they have the property of being mine. On this view, the topography of mental space is given by the existence of a very large number of different properties, one for each person who ever lives. I agree with Madell that I and he could have two simultaneous experiences that were qualitatively identical, but were straightforwardly distinct. But this need not be because one of the experiences has the unique property of being mine, and the other has the unique property of being Madell's. It could simply be because one of these experiences is this experience, occurring in this particular mental life, and the other is that experience, occurring in that other particular mental life. These two mental lives might have to be referred to publicly through their connections to a pair of different human bodies. (The actual cases of divided minds provide an objection to Madell's View. And it does not seem plausible to treat being mine as a property. What distinguishes different particular things or events is not that each has a unique property. Physical things or events can be distinct by being in different places. When I think of my present thought as being mine, I do not identify this thought by reference to a spatial location. My identifying reference (p.518) essentially involves an indexical word, or a demonstrative, rather than the ascription of a unique property. I can use the indexical ‘this’, or the indexical ‘mine’. My claim is that, since I can use the self‐referring use of ‘this’, I do not need to use ‘mine’.)

(37) Some deny that ‘I’ could be explained in a way that uses the self‐referring use of ‘this’. For an argument supporting the view that I accept, see RUSSELL.

(38) I follow SHOEMAKER (1), p. 22.

(39) QUINTON, in PERRY (1), p. 60.

(40) WIGGINS (1), p. 50. I decided to study philosophy almost entirely because I was enthralled by Wiggins's imagined case.

(41) Cf. WIGGINS (1), p. 40. I owe this suggested way of talking, and one of the objections to it, to Michael Woods.

(42) See Lewis's ‘Survival and Identity’ and my ‘Lewis, Perry, and What Matters’, both in RORTY.

(43) Other Reductionists with whom, on the whole, I agree include H. P. Grice (in PERRY (1)), A. J. Ayer (see especially ‘The Concept of a Person’), in AYER (1), A. QUINTON, J. L. Mackie, (in MACKIE (4) and (5)), J. Perry, especially in ‘The Importance of Being Identical’, in RORTY, and in PERRY (2), D. K. Lewis (in RORTY), and S. Shoemaker (in his Personal Identity, Blackwell, 1984).

(44) REID, in PERRY (1), p. 114.

(45) In WILLIAMS (9), reprinted in WILLIAMS (2), pp. 19‐25.

(46) SHORTER; and J. M. R. Jack (unpublished), who requires that this criterion be embedded in a causal theory.

(47) WILLIAMS (2), p. 20.

(48) WIGGINS (1), (2), and (3) advance similar arguments. Some of the issues raised, which I do not discuss here, are crisply discussed in NOZICK (3), pp. 656‐9.

(49) WILLIAMS (2), p. 23.

(50) Cf. WIGGINS (1), p. 55

(51) WIGGINS (4), p. 146. As we shall see below, some writers reject this claim.

(52) WILLIAMS (9), reprinted in WILLIAMS (2), p. 24.

(53) In WIGGINS (3). Sadly, Wiggins does not here continue his discussion of his imagined case of division in WIGGINS (1).